Lighting apparatus, for example used for back-lighting of LCD-displays, usually emit polychromatic light, such as light with a color location in the white region of the CIE-diagram. For the generation of polychromatic light, lighting apparatus usually comprise primary light sources emitting light with different colors, which is mixed additively to produce the desired polychromatic light. In order to control brightness and color location of the polychromatic light, the primary light sources of the lighting apparatus have to be controlled.